Semiconductor device including bipolar transistor and buried conductive region

Abstract

A semiconductor device and a method for manufacturing the device using a semiconductor substrate of a high resistance with improved Q value of a passive circuit element. Leakage current due to an impurity fluctuation, in the high resistance semiconductor substrate and noise resistance of an active element in the high resistance semiconductor substrate are improved. The semiconductor device includes a bipolar transistor at a main surface of and in the semiconductor substrate. The bipolar transistor includes a semiconductor layer of a first conductivity type at a bottom portion of the bipolar transistor and the semiconductor device includes a buried layer of a second conductivity type, located in the semiconductor substrate and facing the semiconductor layer of the first conductivity type.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly to a semiconductor device wherein a silicon substrate of a high resistance is used to secure the Q value of passive elements and to restrict leakage current to the substrate so that noise between elements can be reduced, and a method for manufacturing the same.[0003]2. Description of the Background Art[0004]As mobile terminal apparatuses, such as cellular phones, have come into wide use, the manufacture of high frequency devices at a lower cost has become required. Therefore, research has been carried out concerning the replacement of MMICs (Monolithic Microwave Integrated Circuits), wherein the expensive compound semiconductor GaAs is used, with MMICs or Bi-CMOSs (Complementary Metal Oxide Semiconductor) that use silicon (Si) as a base.[0005]Si into which n conductive type or p conductive type impuriti...

AI Technical Summary

Benefits of technology

[0010]An object of the present invention is to provide a semiconductor device and a manufacturing method for the same wherein a semiconductor substrate of a high resistance is used so that the Q value of the passive circuit elements can be enhanced, wherein leak current due to impurity fluctuation that easily occurs in such a high resistance semiconductor substrate is restricted and wherein noise resistance of active elements in the high resistance semiconductor substrate is increased.

[0012]According to this configuration, a barrier potential against carriers can be formed by providing a predetermined potential to the buried layer of the second conductive type in the case that the above described first conductive layer is use as, for example, a buried collector region or a buried base region. Therefore, even in the case that, for example, a semiconductor substrate of a high resistance, of which the impurity concentration is very low, is used and an impurity concentration fluctuates so that the conductive type fluctuates in the process of manufacture of a semiconductor device, such a barrier potential can prevent leak current from leaking from this buried collector region or this buried base region to the substrate.

[0014]In addition, a predetermined potential can be provided to the above described buried layer of the second conductive type from the outside as the above described barrier potential. In the case that an active element is provided in addition to the above described bipolar transistor, the electric flux lines of the transistor can be confined in a narrow range by this potential. As a result of this, noise resistance of the semiconductor device can be increased. In the case that a high resistance semiconductor substrate is not used, such noise resistance can be expected to a certain degree and the noise resistance can be further increased by the above described buried layer of the second conductive type.

[0016]According to this configuration, in the case that a vertical bipolar transistor, for example, is formed including the first to the third semiconductor layers wherein the first semiconductor layer is used as a collector region, leak current from the collector region can be prevented by providing a potential that becomes a barrier potential to the buried layer of the second conductive type. In addition, in the case that an active element is included in addition to the above described bipolar transistor, the electric flux lines of the above described bipolar transistor can be confined in a narrow range so that noise resistance can be increased.

[0018]According to this method, a predetermined potential is supplied to the buried layer of the second conductive type and, thereby, leak current can be prevented from leaking from the lower portion region of the first conductive type of the bipolar transistor to the semiconductor substrate even in the case that the conductive type or the like, fluctuates during the process due to the very low impurity concentration of the semiconductor substrate.

Problems solved by technology

Therefore, it is difficult to form capacitors or inductors having Q values that are sufficiently large in high frequency regions by using an Si substrate.

In the case that a high resistance substrate, as described above, is used, however, the following problems arise.

Therefore, there is a risk that leakage current will increase from a collector region to the substrate in an element due to unexpected fluctuation in impurities and, thereby, the yield of the elements is lowered.

Therefore, the spread of electric flux lines from the elements becomes great in the lateral direction and there is a problem that the influence of noise between elements will becomes large when active elements are integrated at a high density.

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